The Royal High School. Picture: Jon Savage

Her family’s Dunard Fund, which been one of the most important private donors of the Edinburgh International Festival in recent years, is behind the creation of a new charitable trust aiming to create a “fitting and lasting legacy” for the celebrated landmark.

Her husband, the filmmaker Murray Grigor, has already made a short film calling for educational or cultural uses to be found for the building, which dates back to 1829. He has said that designs for the proposed hotel development look like “something out of Las Vegas.”

The new charity has already lodged outline plans with the city council - which has a deal in place for more than five years to lease out the building as a hotel - for the building to become home to the specialist music school, which is said to have “outgrown” its current home in the capital.

However the new charity’s frontman, Willie Gray Muir, has also spearheaded one of the most controversial developments in modern times in Edinburgh.

St Mary’s Music School would breathe life into the building again, filling the rooms with music - a literal rejuvenation of Thomas Hamilton’s world-class monument of the Edinburgh Enlightenment

Gray Muir

Councillors approved a huge housing development in the grounds of Edinburgh Napier University’s former Craighouse campus last September in the face of more than 1,300 objections.

There has been a storm of protest over plans to create two major extensions at either side off the existing building on Calton Hill to accommodate the hotel plans.

But backers of the alternative scheme insist their scheme will be “in keeping with Edinburgh’s rich cultural and historical heritage, but also presents an economically sustainable future.”

The new Royal High School Preservation Trust, which a number of cultural, education and heritage figures are involved with, said the plans for the building would “restore its original use” and become a place for educating young people from across Scotland and beyond.

A statement announcing its plans said the charity had the “financial backing of the philanthropic Dunard Fund, which has committed funds to underwrite the restoration of the old Royal High School’s listed buildings and provide world class facilities for the music school.”

Gray Muir, who has been appointed chair of the charity, added: “Our aim is the preservation and enhancement of an endangered architectural masterpiece, not just in the context of the City of Edinburgh but Scotland as a whole.

“Our ardent wish is to achieve this by maintaining the Old Royal High buildings as a school, the purpose for which they were built, and ensure its future use as a vibrant and unique academic institution.

“What could be more appropriate than making it home to a national treasure like St Mary’s Music School?

“St Mary’s Music School would breathe life into the building again, making full and imaginative use of its wonderful spaces, filling the rooms with music - a literal rejuvenation of Thomas Hamilton’s world-class monument of the Edinburgh Enlightenment.

“We look forward to outlining our detailed plans for the site soon.”

As well as Mr Gray Muir and Ms Colburn Grigor, others involved include Richard Austin, a trustee of the Architectural Heritage Society of Scotland and a former pupil of the Royal High School, Ray Entwistle, a former chairman of the Scottish Civic Trust, and Colin Liddell, chair of Pitlochry Festival Theatre.

Entry to St Mary’s, Scotland’s only independent specialist music school, which is open to 9-19 year-olds, is by audition and assessment, based on musical ability and potential. Scottish Government funding of up to 100 per cent is available to help with the cost of tuition and boarding fees.

Headmaster Kenneth Taylor said: “It is part of St Mary’s Music School’s vision for the future that we have a building which enables us to have both teaching and performance space.

“The board is actively considering whether this should be an extension at our existing premises or a move to another building in Edinburgh that could accommodate this.

“The possibility that the school could move to the former Royal High School Building is an unexpected development but a welcome one.

“St Mary’s Music School is not just a school for Edinburgh, but one for the whole of Scotland with our pupils coming from across the nation and beyond, and all taken on musical ability regardless of personal circumstances.

“It is very early days and we will have to see what happens but perhaps it is fitting that a landmark building should become the home of a national institution.”

Dunard Fund trustee Peter Thierfeldt said: “Our mission is to create world-class opportunities for musical talent and support the preservation of magnificent architecture. This project offers the realisation of both.

“It is our desire to make a lasting impact on the cultural heritage of Scotland and we’re delighted to give our backing to the trust, with its goals to conserve the former Royal High School for St Mary’s Music School.”

David Orr, co-founder of the Urbanist Group, one of two developers pursuing the hotel scheme, said: “We are proceeding with the agreement with the council to restore the old Royal High School into a world-class hotel.

“With £55 million committed from an institutional group of investors, this is a fully-funded project which will not require a penny from the public purse.

“Furthermore, when operational the hotel will support 640 local jobs a year and contribute £26.7 million to Edinburgh’s economy annually, as well as give the public full access to the building for the first time.”